All clinical laboratories, and many medical, biological and industrial laboratories make use of a reusable hemocytometer for measuring the concentration of particles in suspension. Such measurement is commonly made for blood cells, bacteria, cells from tissue culture, washings, scrapings and the like.
Particle concentration=number of particles/unit volume of suspension. Thus, one must be able to define precisely both of these quantities, number and volume.
The traditional hemocytometer, standard on a worldwide basis, is a volumetric slide having a specimen chamber of great accuracy. However, the traditional hemocytometer is quite costly to manufacture involving precise grinding and etching of glass, is fragile, and requires thorough washing after each usage in the laboratory. This washing is quite expensive on a commercial basis. Even more importantly, the traditional prior art device is not well suited to mechanized high speed measurement of concentration. It does, however, possess a true precision volumetric chamber formed integrally therein in terms of area and depth on x, y and z axes.
The objective of the present invention is to provide a very inexpensive disposable or single-use volumetric slide which may be employed for the purposes of the traditional reusable hemocytometer or slide, but without the high cost of manufacturing and necessity for washing. The device of the invention is constructed of standard low cost components which in assembled relationship form a volumetric slide having a chamber or chambers of high precision depth on the z axis comparable to the precision depth of the chamber afforded by the expensive hemocytometer.
In contrast to the prior art, the chamber area parameters are not provided or inscribed integrally on the slide but are determined with great accuracy by use of a simple optical magnification system employed in conjunction with the disposable slide. In this optical system, the x-y axis measurements of the precision slide volumetric chamber are optically projected on a reference plane or screen, following which the volume of the slide chamber can be calculated with great accuracy, followed by precision determination of particle concentration.
In effect, the use of the inexpensive disposable slide with integral precision chamber depth when used in the magnifying optical system enables the ready determination of what may be termed "a precision synthetic area" and "a precision synthetic volume" through simple multiplication of x, y, z axis dimensions with a magnification factor included in the computation.
Among the advantages inherent in the single use disposable slide structure and method of use are:
(1) The coverslip is of standard thickness glass for which the microscope objectives have been designed, thereby improving the optical quality of images.
(2) The slide base plate is a standard flat glass microslide whose thickness is designed into the condenser optics, again improving optical quality.
(3) The slide assembly is so inexpensive that it can be discarded after the test, saving the not inconsiderable cost of washing, and obviating any possibility of specimen carry-over from test-to-test, as can sometimes occur in the prior art.
To comply with the duty to disclose any known prior art under 37 C.F.R. 1.56, the following prior U.S. Pat. Nos. are made of record herein: 3,551,023, 3,556,633, 3,656,833, 3,777,283, 4,022,521.